RIOS : Radar Inlet Observing System
Assessing navigability of tidal inlets
Challenges to maintaining safe, navigable tidal inlets across the US while minimizing deleterious effects to adjacent property and the environment, can be daunting and often encompasses many government agencies and stakeholders with varying interests and missions. When this maintenance requires dredging of the navigation channels, the US Army Corps of Engineers is typically the responsible agency, while the US Coast Guard dictates placement of the various aids to navigation. These missions alone, and there are many others, are difficult to accomplish on a continual, up-to-date basis across many of our shallow, wave-dominated tidal inlets because the position of the channels and associated shoals can be incredibly dynamic, and the volume of infilling sediment can stretch available resources. The Radar Inlet Observing System (RIOS) is designed to provide near real-time navigation and engineering support at tidal inlets over extended, hourly time periods, and to do so cost-effectively in remote locations. Specific RIOS products include shoal migration and encroachment into navigation channels, breaking wave conditions around the navigation channel, surface currents, and sediment transport pathways over event and seasonal time scales.
Leland MI

Present location:

Navigation Support
Breaking and shoaling wave conditions over the shoals and navigation channel.
RIOS Bathymetry
Bathymetry determined from RIOS-measured wave speed and inversion of the linear dispersion relationship.
Bedform Migration


5 Day

Long Term

Hourly, de-tided image of bedform morphology and position, resolved from measured radar intensity of shoaling and breaking waves (left panel, A), and average bedform migration (m/day) determined from hourly data spanning 5 days (middle panel) and the extent of deployment (long-term panel).
Documentation and References
McNinch, J. E.; Brodie, K. L.; Slocum, R. K., RADAR INLET OBSERVING SYSTEM (RIOS): CONTINUOUS REMOTE SENSING OF WAVES, CURRENTS, AND BATHYMETRY AT TIDAL INETS, Proceedings of the 2012 Oceans Conference in IEEE Xplore, Norfolk, VA.
McNinch and Humberston, 2019, Radar Inlet Observing System (RIOS) at Oregon Inlet, NC: Sediment transport pathways at a wave-dominated tidal inlet, Shore & Beach, Vol. 87, No. 1.

Point of Contact
Dr. Jesse McNinch
Field Research Facility, Coastal Observation and Analysis Branch, CHL 252-261-6840 x243